Wiring Help

[Strokin' 6.0]

I have had problems with my F350, since I bought it. When I plug either our horse trailer or Airstream trailers to the truck, the reverse lights come on, when the truck is running. We have two seven-way plugs on our truck; we have a Herrin Hauler bed, similar to Western Hauler. Both plugs are wired the same way.

I've checked the fuses, #38 and #39, 20A and 15A respectively, and both are fine. I looked under the hood and have the relays in place. I took a test light and checked the individual pins on both plugs. Here is a pic of the plug, as you're looking at it.

Is this correct for Ford? Thanks for the response.

[chuckster57]

Found this. Hope it helps you out:
Marksrv.com 7 way wiring diagram page

[Strokin' 6.0]

Chuck, thanks for the link. I tried a bunch of Google queries and finally came up with what should work. Whoever did the wiring, when my hauler bed was installed switched the red and black wire. In the diagram I found online, it lists the orange wire as auxilliary/reverse lights and black/red for 12v. My truck actually has a red and a black wire, but no orange; turns out the black wire is for the reverse lights and the red is for 12V.

Here's a diagram of how it should be for the 2004 F350 King Ranch....I'm not saying that this is for every year/model, just what I found on mine. The diagram is how you're looking at the wires, after removing the harness from the plug (in essence, you're looking at the back of the plug).

Hope this helps anyone trying to figure it out too.

[westvandude]

Looks like you figured it out. That first one with keyed-on for the center pin is definitely wrong.

Actually, on my trailer tow plug spring snap cover it shows the wiring, which is as you show in your second pic with reverse lights on center pin.

The red "keyed-on" wire would be for charging your auxiliary battery in the trailer. This runs off the relay that's mounted beside the reverse relay. If you do have a battery that powers interior lights in the trailer then make sure this is getting juice when the truck is running.

[Strokin' 6.0]

The horse trailer doesn't have a battery, but the Airstream does; I'll check this afternoon, to make sure that the battery is charging.

Unfortunately, when Herrin installed the hauler bed, they took the original seven-way off, as well as the reverse-aid sensors, and installed Pollack plugs, so I had no diagram to go by.

Thanks for the replies.

[LMJD]

I convert everything over to the heavy truck type Pollak/Berg plugs too, they're better quality.

The horse trailer doesn't have a battery, but the Airstream does;

With a test light and a jumper wire to determine what's what, your constant hot wire can be used as your Airstream batt. charging wire (which includes all your Airstream 12V components), and also for your accessory constant hot for your horse trailer interior tack room lites, exterior lite by the lead rope ties, etc, since they have their own On/Off switches. I have my truck plug wired so it's hot whether the ignition switch is on or not.

[Strokin' 6.0]

Originally Posted by LMJD

I convert everything over to the heavy truck type Pollak/Berg plugs too, they're better quality.

With a test light and a jumper wire to determine what's what, your constant hot wire can be used as your Airstream batt. charging wire (which includes all your Airstream 12V components), and also for your accessory constant hot for your horse trailer interior tack room lites, exterior lite by the lead rope ties, etc, since they have their own On/Off switches. I have my truck plug wired so it's hot whether the ignition switch is on or not.

The only reason I haven't hooked up the Airstream or horse trailer is because we're getting a ton of rain right now, and I have no plans to use either trailer at the moment.

I considered wiring the hot from keyed to constant, but I don't want to run my truck batteries down.

I do have another question, though.....when I had my Dodges, I found out that I had to turn the truck off, before I could plug the trailer to the truck...if I didn't, the towing fuse would blow...happened on my '05 and '01.
Does Ford do the same thing, or can I leave the truck running, while I plug in?

[LMJD]

Does Ford do the same thing, or can I leave the truck running, while I plug in?

I sure can't say since your late model truck has WAY more sofisticated electronics, relays, etc, compared to mine. Matter of fact, the aux wire at the Ford factory harness plug-in behind the bumper was a constant hot in my '91.

I considered wiring the hot from keyed to constant, but I don't want to run my truck batteries down.

I understand. I wanted convenience in my horse tlr, so I wanted constant hot. However, if I'm staying overnite at a rest stop, or rear of a truckstop with my gooseneck tvl tlr and using a lot of lights, etc, I always unhook my trailer plug so I'm just using my tlr batteries. With my bad brain, I always put a note or something on the dash to remind me to plug the tlr back in before I head out in the morning.

[Strokin' 6.0]

I hear ya. I'm already starting to suffer from CRS syndrome!